This invention is generally directed to liquid developer compositions, especially liquid developers with superior transfer efficiencies. More specifically, the present invention is directed to liquid developer compositions comprised of an oil base, pigment particles, black or colored, a stabilizer, and additive components, such as Nuodex Copper Napthenate available from Nuodex Canada Ltd., Sulframin 1298, and Witcamine AL-42, which is commercially available from Witco Chemical Corporation. These additive components assist in both flocculation of the developer compositions, and in wetting of the photoreceptor surface selected. Thus, in one important embodiment of the present invention there are provided liquid inks with acceptable drying times, and excellent transfer efficiencies (percent by weight of the ink composition developed on the photoreceptor and transferred, for example, to paper) of 80 percent or greater, which inks are comprised of oil bases such as Magiesol, pigment particles, a stabilizer component, and as an additive for flocculation of the developer and wetting of the photoreceptor surface surfactants, such as Sulframin 1298, Witcamine AL-42, and Nuodex Copper Napthenate, or mixtures thereof. In a further embodiment of the present invention, there are provided liquid ink compositions comprised of an oil component of, for example, Magiesol or Isopar, pigment particles comprised of black or colored components, inclusive of cyan, magenta, and yellow; a stabilizer component; and as an additive for flocculation of the developer, surfactants such as Sulframin 1298, Witcamine AL-42, and Nuodex Copper Napthenate. The liquid inks of the present invention can be selected for the development of images in various processes, including the liquid development process as described in U.S. Pat. No. 3,084,043, the disclosure of which is totally incorporated herein by reference, xerographic processes, electrographic recording, electrostatic printing, and facsimile systems. In addition, it is known that with traditional lithographic printers there results an ink splitting phenomenon between the printing press and the paper causing unusually low image transfer efficiencies of, for example, less than 60 percent. With the ink compositions of the present invention, this ink splitting phenomenon is substantially reduced enabling transfer efficiencies of 80 percent or greater.
Liquid developer compositions are known, reference for example U.S. Pat. No. 3,806,354, the disclosure of which is totally incorporated herein by reference. This patent illustrates liquid inks comprised of one or more liquid vehicles, colorants, such as pigments, and dyes, dispersants, and viscosity control additives. Examples of vehicles disclosed in the aforementioned patent are mineral oils, mineral spirits, and kerosene; while examples of colorants include carbon black, oil red, and oil blue. Dispersants described in this patent include materials such as an alkylated polyvinyl pyrrolidone. Additionally, there is described in U.S. Pat. No. 4,476,210, the disclosure of which is totally incorporated herein by reference, liquid ink immersion developers containing an insulating liquid dispersion medium with marking particles therein, which particles are comprised of a thermoplastic resin core substantially insoluble in the dispersion, an amphipathic block or graft copolymeric stabilizer irreversibly chemically, or physically anchored to the thermoplastic resin core, and a colored dye imbibed in the thermoplastic resin core. The history, and evolution of liquid developers is provided in the '210 patent, reference columns 1 and 2 thereof.
In addition, there is illustrated in U.S. Pat. No. 3,844,966 liquid toner compositions comprised of a carrier liquid with toner particles suspended therein, and a trivalent or tetravalent metal salt of an organic acid, and an organic amine dissolved in the carrier liquid, reference for example the Abstract of the Disclosure. British Patent Publication No. 1,537,211 is directed to aqueous printing inks with improved transfer efficiencies, which inks contain, for example, polyethylene oxides of a molecular weight of from about 100,000 to 350,000; while Japanese Patent Publication discloses electrophotographic liquid developers containing lecithin in an organic amine, reference the Abstract of the Disclosure. The aforementioned prior art, however, does not teach liquid developer compositions as illustrated in the present invention wherein, for example, there is selected a stabilizer and additive components such as Nuodex, which components enable the flocculation of the developer compositions, for example, and thereby provide for improved transfer efficiencies of the image developed.
Although the above described prior art liquid inks are suitable for their intended purposes, there remains a need for new liquid developers. More specifically, there is a need for liquid developers with improved drying times, superior transfer efficiencies, and desirable conductivity values. There also is a need for colored liquid developers which possess many of the aforementioned characteristics. Additionally, there is a need for economical liquid developer compositions that permit images of excellent resolution in a number of known imaging processes, including those illustrated in U.S. Pat. No. 3,084,043, the disclosure of which is totally incorporated herein by reference. Moreover, there is a need for liquid developers wherein the colorants selected are suitably dispersed such that the primary particles are of an average diameter of from 0.1 micron to about 5 microns thereby enabling black, or colored images of excellent resolution. Further, there remains a need for liquid developers wherein there is included therein certain additives that enable flocculation of the developer, and wetting of the photoreceptor surface thus permitting transfer efficiencies of 80 percent or greater. There also is a need for liquid inks which are useful with dielectric papers. In addition, there is a need for developers having incorporated therein viscosity additives such as soluble polymers or viscosity modifiers such as clays and silicas permitting inks with a preferred viscosity of from about 200 to about 300 centipoises, which viscosities are not time dependent as is the situation with known thixotropic inks. Furthermore, there is a need for ink compositions with a preferred resisitivity not exceeding 10.sup.11 ohm-cm. Accordingly, there is a need for ink compositions with a resistivity of from about 10.sup.9 to about 10.sup.11 ohm-cm thereby preventing image distortion. Additionally, there is a need for ink compositions that are conductive, can be easily cleaned from the photoreceptor surface, will wet the photoreceptor surface and the gravure roll containing the ink; possess extended shelf life, for example about 18 months, which inks are further free of environmentally hazardous materials. These and other needs are obtainable with the ink compositions of the present invention.